I assume it's just new toy syndrome (I have a D100 I bought in 2002, the 700 is looking really nice!). I'm not sure what features of the new camera would require new lenses...convince me .

On choosing lenses, my decision criteria would be:
- As was mentioned below, the autofocus will be faster and not hunt as much with a 2.8. This is not as important on the shorter focal lengths. This is the biggest PITA for me on my existing lenses.
- The 2.8 helps on the wide lenses if you like to use a polarizer as you lose 2 stops.
- The DX lenses will be thrown away as more of us get FX formats.
- The VR is only important at longer focal lengths.
- I try to make the filter sizes compatible with what I already have (77mm).
- On my trips, I keep the long lens on the camera, usually the surprises that require a fast shot need a longer lens. There is usually time for the wide angle shots to switch lens. I also don't see the point in having an SLR if you want one all-purpose lens.

In my dream world of "flexible budgets", I would go for multiple lenses in this order:

1) 24-70 2.8G ED AF-S (Have a cheap one in this category - would like to upgrade)
2 ) 70-200 f2.8G AF-S VR (Have the non-VR version, my fave!)
3) 14-24 2.8G AF-S (or maybe the 17-35 2.8G)